This invention relates to an apparatus for sharpening saw blades. In particular the invention relates to an apparatus for sharpening band saw, frame saw or circular saw blades.
The invention will be described by way of example with reference to sharpening band saw blades although, as mentioned above, it may equally be employed for sharpening other saw blades. The apparatus of the invention may also be used for manufacturing saw blades from blade material.
The teeth on a saw blade have a tip portion, a leading edge or front portion and a trailing or back portion. Gullet and throat portions are typically located between the back portion and front portion of the tooth. The angle the front portion makes to the vertical is called the hook angle and different hook angles are adopted for cutting different materials.
A blade may have a plurality of teeth with each tooth of the same profile. The teeth may be square cut or bevelled to one side or other of the blade. In some instances the teeth may be bevelled on both sides and have a pointed tip. Where the teeth are square cut the tip may be flat and have a cutting edge extending normally to the blade. It is not unusual for a blade to have a series of differently shaped teeth alternating in a repeating sequence along the blade. In addition, blades may have a variety of pitch distances between teeth.
Prior machines for sharpening blades have a cutting head with a grinding disk. The head was reciprocally movable either by the provision of a slide or an arm pivoted to the machine. The pivot axis was generally parallel to the side faces of the blade or the head was moved reciprocably relative to the blade during grinding.
In such machines the mechanism for adjustment to achieve different hook angles or tooth profile (square, single bevel or double bevel) was difficult to achieve and hence the machines were complex and expensive.
U.S. Pat. No. 4,018,109 discloses a machine where the cutting head was mounted for movement on a slide. That specification is primarily concerned with the manner in which blades with wide pitch distances and variations in pitch distances could be advanced through the machine.
U.S. Pat. No. 4,018,107 discloses another machine for sharpening saw blades having teeth of alternative high and low profiles.
U.S. Pat. Nos. 3,960,037, 4,136,585 and 4,436,000 are exemplary of machines where the head is reciprocated transversely of the blade to grind the teeth of the blade.